Power cables often include conductors which are insulated by paper tapes impregnated with oil which is maintained under pressure and protected by an oil-tight sheath of lead or aluminum. The oil pressure is about 15 bars for cables intended for laying in the seat to depths of about 100 meters, thereby compensating for loss of head in the oil channel and balancing the static pressure to which the cable is subjected at the water bottom.
Cables of the type having two layers of armoring are such that the oil-tight sheath of lead or aluminum is surrounded by two coaxial layers of armoring, namely inner armoring and outer armoring. The inner armoring for traction or carrier purposes is frequently constituted by a layer of steel wires wound around the sheath at a long pitch, while the outer armoring for providing protection is often constituted by steel wires wound at a short pitch.
When it is necessary to make a splice between two lengths of cable, there are several ways of proceeding. One of these ways consists of enclosing the connections between the various electrical conductors in a rigid housing which is bonded to the oil-tight sheaths of the two-lengths of cable to be joined. The inside of the rigid housing is then put under oil pressure, and the splice is terminated with all of the necessary protective layers around the housing and around the oil-tight sheaths in the vicinity of the housing. This technique is suitable for making repairs or for connecting together two lengths of cable which are intended to remain at the bottom of the sea, however it suffers from the drawback of impeding cable handling, should the cable ever be moved or raised from the bottom back to the surface. The presence of a rigid housing makes it difficult to wind the cable on a drum or in the hold of a boat.
Patent documents FR-A 2 555 372 or GB-A 2149981 also describe making a flexible splice for submarine cables of the above type by replacing the lead or aluminum oil-tight sheaths over the splice with a cylindrical envelope having corrugated walls, which envelope is bonded to the sheaths via rigid connection pieces. However, the increase in the outside diameter of the cable at the splice remains considerable, and this type of splice is not suitable for a submarine cable with two layers of armoring, and in particular it is not suitable for cables having outer protective armoring at a very short pitch.
The present invention seeks to provide a flexible splice for an impregnated paper submarine cable which includes at least one layer of armoring, with the outside diameter of the splice being less than in the prior art and with the splice being capable of being subjected to the same handling as the cable, both at sea and in the factory.